I've been working on some add-Ins, and I'm having a good time of it. However, I could do so much more if you guys would expose some events that would let my add in know that a sketch needs to be recomputed, or if a parameter changed - at a minimum.
Other nice to haves would be more functions that the user has, but isn't available to the api (like adding fitPoints to a spline, but that can be worked around, somewhat).